The present invention relates to a novel inductive thin-film magnetic head for a dual-element thin-film magnetic head unit including an inductive thin-film magnetic recording head and a magnetoresistive reading head.
With the recording density of a magnetic disk apparatus ever on the increase, magnetic coercive force of the magnetic recording medium is increased while the track width of the inductive thin film magnetic head used for recording is decreasing. Also, the downsizing of the magnetic disk apparatus has reduced the reproduction output of the inductive thin-film magnetic head. For this reason, an inductive thin-film magnetic head is used as a recording head, and a magnetoresistive head is used for converting the leakage magnetic field from the medium as a resistance change. The magnetoresistive head includes a sensor constituted of a magnetoresistive element, a giant magnetoresistive element, a ferromagnetic tunnel junction element, etc., and one of the magnetic shields for improving the spatial resolution is shared with one of the magnetic cores of the inductive thin-film magnetic head.
The current trend of the shape of the magnetic core along the air-bearing surface of an inductive thin-film magnetic head is such that the width of the upper magnetic core determines the track width and the width of the lower magnetic core serving also as the upper shield film of the reproductive head is several tens of times larger than the track width. With the decrease in track width, however, the magnetic field expanding out of the track ends has become conspicuous.
In order to solve this problem, the structure of an inductive thin-film magnetic head with the upper portion of the lower magnetic core of the inductive thin-film magnetic head is shaped to the same width as the upper magnetic core is described in U.S. Pat. No. 5,438,747. Also, the structure of the inductive thin-film magnetic head having a trench including a pole tip layer with the width thereof defining the track width is described in JP-A-7-296328 laid open Nov. 10, 1995 and corresponding to the U.S. patent application Ser. No. 229,484 filed Apr. 19, 1994.
The inductive thin-film magnetic head described in U.S. Pat. No. 5,438,747 (JP-A-7-262519) and JP-A-7-296328 has a protrusion structure having substantially the same width as the track in the neighborhood of the air-bearing surface in the upper portion of the lower magnetic core. This protrusion structure facilitates the machining of the track to a width in the order of submicrons, and the magnetic fields are concentrated in the protrusion structure.